Starches are clean.
Starches are nutritionally complete.
Starches have loads of protein.
They are full of fiber.
They are very satisfying.
They are loaded with vitamins and minerals.
Potatoes and sweet potatoes have all the vitamins and minerals you need except for B12. [See Kon All Potato Diet]
Grains and legumes are missing two vitamins: A & C. Add broccoli to your rice then you would have all the A & C you need.
If you add oil, it can dilute out the nutritional value of the potato.
All large populations of trim, healthy people, throughout all verifiable human history have obtained the bulk of their calories from starch.
Archeological findings reveal approximately 6,000 year history of starch based diets:
Barley in the Middle East
Corn (maize) in North, Central, and South America. Aztecs and Mayas are known as people of corn.
Legumes in Americas, Asia, and Europe
Millet in Africa
Oats in Middle East
Potatoes in South America. Incas later changed to quinoa. It was a food of greater strength when they went to battle.
Sorghum in East Africa
Sweet Potatoes in the South America
Rice in Asia.
Rye in Asia
Wheat in the Near East. It was the Pharaohs who lived on rich foods who got to be mummies. They got the diseases.